Amorphous carbon or diamond-like carbon ("DLC") coatings have been used to coat a number of different surfaces that encounter frictional contact and wear during use. DLC is chemically inert and is known to have a low coefficient of friction. DLC coatings also have been shown to be extremely smooth, unlike polycrystalline diamond deposits.
In some applications, it is desirable to coat the DLC with a lubricant film, typically a perfluorinated lubricant film, to further decrease friction and wear. For example, lubricant films are desirable for magnetic recording media.
Magnetic recording media generally are comprised of a magnetic coating material deposited on a permanent substrate. The magnetic coating material usually consists of a binder having ferromagnetic materials therein, or a metallic layer comprising a magnetic material. An example of a magnetic recording media is a hard disk having a substrate of aluminum or silicon and a magnetic metallic coating thereon, which can be an alloy such as GdCo, CoPtCr, CrV--CoPtCr, etc.
Magnetic recording media are used in combination with magnetic recording heads or transducers to produce read, write, and erase functions. As the technology has developed, the thickness of the magnetic metallic layer has decreased and the "density," or the total number of bits that can be stored on the magnetic recording medium, has increased.
Higher density recording has required that the recording heads be brought into closer and closer physical contact with the metallic magnetic recording layer. Very often, this results in "crashing" of the recording head into the magnetic recording medium. "Crashing" results in wear on the magnetic metallic layer and on the surface of the magnetic recording head. Crashing also may destroy data that is stored on the metallic magnetic recording layer.
In order to prevent crashing, an ultra-thin (less than 200 .ANG., or less than 20 nm) protective layer of DLC has been provided to make the magnetic recording layer abrasion-resistant. In order to even further decrease friction and wear, the DLC has been coated with an even thinner film of lubricant, typically a perfluorinated lubricant.
The bond between the storage medium and the DLC coatings generally has been strong; however, the bond between the DLC coatings and the lubricant films has been weak. Research has shown that perfluorinated lubricants do not chemically bond to DLC, but are bound to DLC coatings by mere van der Waals forces. As a result of the weak attraction between the DLC and the lubricant, it is possible for a lubricant film to fail upon high-velocity impact with a slider head.
A means is needed to provide stronger bonding between DLC and a lubricant coating.